docs: async def increment(self, key, delta=1, namespace=None, _conn=None):
          """
          Increments value stored in key by delta (can be negative). If key doesn't
          exist, it creates the key with delta as value.
  
          :param key: str key to check
          :param delta: int amount to increment/decrement
          :param namespace: str alternative namespace to use
          :param timeout: int or float in seconds specifying maximum timeout
              for the operations to last
          :returns: Value of the key once incremented. -1 if key is not found.
          :raises: :class:`asyncio.TimeoutError` if it lasts more than self.timeout
          :raises: :class:`TypeError` if value is not incrementable
          """
          start = time.monotonic()
          ns_key = self.build_key(key, namespace=namespace)
          ret = await self._increment(ns_key, delta, _conn=_conn)
          logger.debug("INCREMENT %s %d (%.4f)s", ns_key, ret, time.monotonic() - start)
          return ret